Note: I havn't test this properly yet. Let me know if there are any issues.

It works BUT:
after the time has expired, a player is still protected from friendly fire damage.
It means that if after 20 seconds (according to the cvar you posted) I shoot a team mate, the damage is reflected to me but he's not actually taking any damage.
They should take the damage, and it should be MIRRORED to me.
If i attack a mate and the damage is 10 hp, we should both get 10 hp removed from our health (this assuming the damage ratio is 1.0 ofc)
But it's not happening right now. it's like if friendly fire is just reflected to the attacker but not taken by the victim.
Was the plugin supposed to work like this?

So: killshotreverse_blockvictimdamage being set to 0 would mirror damage (both attacker and victim receive damage)
And: killshotreverse_blockkillshotsonly being set to 0 would mirror all friendly fire damage, not just killshots.

So: killshotreverse_blockvictimdamage being set to 0 would mirror damage (both attacker and victim receive damage)
And: killshotreverse_blockkillshotsonly being set to 0 would mirror all friendly fire damage, not just killshots.

Cool! So have you already pushed the update? Let me see the github page